A poly(l-glutamic acid)/β-cyclodextrin (P-l-Glu/β-CD)-modified glassy carbon electrode (GCE) was prepared by electrochemical polymerization of l-glutamic acid on GCE and subsequent self-assembly of β-CD onto the obtained P-l-Glu. Electrochemical recognition of tryptophan (Trp) enantiomers with the P-l-Glu/β-CD was investigated by differential pulse voltammetry (DPV), and the results show that Trp enantiomers can be effectively recognized at the P-l-Glu/β-CD-modified GCE. It is also interesting to find that temperature plays a crucial role in the enantioselective recognition, which is evidenced by the variable-temperature UV spectra of the inclusion complexes of Trp enantiomers and β-CD. Under optimum conditions, the oxidation peak current ratio of l-Trp to d-Trp could reach 2.30, which is attributed to the stereoselectivity of β-CD to the enantiomeric pair of Trp.
Interfaces between immiscible glassy homopolymers are normally weak as there are few chains which can penetrate far enough into the opposite side of the interface to become entangled there. To overcome this problem a number of strategies for strengthening can be pursued, all of which involve adding a third polymeric component to the system, which either segregates to or reacts at the interface. We have examined the effect of small additions of diblock copolymers, random copolymers and reactive end-functional chains in to interfaces between polystyrene and other glassy polymers on the interfacial fracture toughness. By labelling portions of the polymer additive with deuterium, we can use forward-recoil spectrometry on the fracture surfaces to determine (1) the areal chain density, Σ, of the additive at the interface and (2) the mechanism of interface failure. We outline how the important failure mechanisms, chain pull-out, crazing and chain scission, depend on Σ and the architecture of the polymer additive and discuss strategies for maximizing the interfacial fracture toughness.
A facile one-step approach was adopted for the electrochemical deposition of cubic nickel hexacyanoferrate/polyaniline hybrids (NiHCF/PANI) on graphene electrode which played an important role in the electrocatalytic polymerization of aniline. NiHCF was hybridized into PANI based on the unique doping property of PANI. The obtained hybrids were characterized by cyclic voltammetry (CV), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). The non-enzymatic sensor based on the NiHCF/PANI hybrids presented significant electrocatalytic performance toward the oxidation of glucose, because PANI films on graphene could greatly increase the immobilized amount of the redox couple of Ni(OH)2/NiOOH. The enzyme-free sensor showed excellent analytical performance and high selectivity with no interferences from other oxidizable species. The as-prepared sensor was further applied for the assay of glucose in real samples, and the results demonstrated its potential as a sensitive glucose sensor.
Objective: To investigate the effects of Mindfulness-Based Stress Reduction (MBSR) on the perceived stress of intern nursing students. Methods: A total of 151 intern nursing students from 3 first-class hospitals in Guangdong Province, China, were selected for an 8-week MBSR training program and randomly divided into two groups, including a control group (n=86) and an intervention group (n=65). The two groups were evaluated by the Self-Rating Anxiety Scale (SAS) and the Chinese Nurse Job Stressors Questionnaires (CNJSQ) a day before the intervention and at the end of the 8-week intervention period. Results: After the intervention, the SAS and CNJSQ of intern nursing students decreased significantly compared with those before the intervention (P<0.05). Conclusion: MBSR training alleviates the perceptual pressure of nursing students in clinical practice to some extent, improves their satisfaction with nursing work, actively mobilizes work motivation, and widely applies MBSR in clinical nursing work, which has feasibility and practical significance.
Aluminum tube used to evaporator in refrigerator or ice tank was passivated on line by the solution of organic acid ester inhibitor A of corrosion in whose molecule there is a long line alkyl.Corrosion resistance of passivated aluminum tube was tested by method of release hydrogen,salt fog and electrochemistry,and these result proved that the passivated aluminum tube had excellent ability of corrosion resistance.The passivation time of this passivator solution was less than 5 second,and there was not any heavy metal and fluorid.The passivated aluminum could meet the ROHS standard of Europel,and was invaluable in domain of industry application.
Aluminum tubes pretreated by γ-NH2(CH2)3Si(OCH2CH3)3 were online passivated with a solution of organic acid ester corrosion inhibitor A with long-chain alkyl.Tests of hydrogen evolution,salt spray and electrochemistry proved that these aluminum tubes passivated by this method had excellent corrosion resistance.This passivating solution needed only less than 2 seconds to have aluminum passivated,and there was no any heavy metals and fluoride in this solution.It meets the requirements of ROHS standard of Europe.
Bis-[-3-(triethoxysilyl)propyl] tetrasulfide(a kind of silane,abbreviated as BTESPT)and an organic acid ester with long chain alkyl group(inhibitor A throughout)were used to synergistically passivate aluminum.Thus the Al samples were sequentially immersed in the silane(BTESPT)solution and inhibitor A solution,allowing the formation of compact hydropho-bic complex film on the surface of the Al surfaces.The final syn-ergistic passivation film was obtained by drying the hydrophobic complex film at 100℃ for 12 h.The corrosion resistance of the synergistic passivation film was evaluated using hydrogen-evolution test,weight loss test in alkaline solution,salt-fog test,and electrochemical test.The microstructure of the passivation film was examined by means of scanning electron microscopy(SEM),and the film-formation mechanism and the corrosion resistant mechanism of the film were discussed.It was found that the complex passivation film had excellent corrosion resistance.No heavy metals and fluorides were detected in the composite passivation film,meeting the requirements of European ROHS standard.
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